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-= Operator, confused with output result

I was recently tracing a line of code:

x -= 353 - 350

However, the answer came up to be -3.

To my surprise, I figure the -= operator would follow as:

x = x - 353 - 350

which then would equal to -703

Why is the actual answer -3 and not -703?

I was searching for reference on this website: http://www.adobe.com/devnet/actionscript/learning/as3-fundamentals/operators.html

The example it gave led me to believe that the operator -= should produce -703.

var x:uint = 5; x -= 5; // x is now 0

Wouldn't the above example represent how x = x - 5 is 0? Or is there an alternative code/logic that I'm missing?

Solution

  • Operator precendece:

    https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Operators/Operator_Precedence

    -= has precedence of 3, while + and - have precedence 13 (higher),

    so the code executes as the equivalent of

    x -= (353 - 350)
x -= (3)
x -= 3;
x = x - 3;

    And as per basic mathematics:

    x -= (353 - 350)
x += -(353 - 350)
x += (-353 + 350)
x += (-3);